The manipulation of fluids to form fluid streams of desired configuration, discontinuous fluid streams, droplets, particles, dispersions, etc., for purposes of fluid delivery, product manufacture, analysis, and the like, is a relatively well-studied art. Examples of methods of producing droplets in a microfluidic system include the use of T-junctions or flow-focusing techniques. However, such techniques often work only at relatively slow laminar or “dripping” conditions, and in some applications, faster rates of droplet production are needed, for instance, to produce larger numbers of droplets.